There has been proposed a semiconductor device having an IGBT region in which an IGBT device is formed as a switching device used for an inverter or the like, and a diode region in which a diode device is formed (refer to Patent Literature 1, for example).
Specifically, the semiconductor device includes a base layer formed on the surface of a semiconductor substrate making up an N−-type drift layer and a trench gate structure passing through the base layer. A P-type collector layer and an N-type cathode layer are formed on the back side of the semiconductor substrate, where an N-type emitter region is formed in an area of the base layer located above the collector layer. An upper electrode electrically connected to the base layer and the emitter region is formed on the front side of the semiconductor substrate, while a lower electrode electrically connected to the collector layer and the cathode layer is formed on the back side of the semiconductor substrate. That is, the IGBT region corresponds to a region in which the collector layer is formed on the back side of the semiconductor substrate, while the diode region corresponds to a region in which the cathode layer is formed on the back side of the substrate. In other words, a boundary between the collector layer and the cathode layer is a boundary between the IGBT region and the diode region in the aforementioned semiconductor device.
A damaged region is formed on the surface of the diode region of the semiconductor substrate by irradiating the entire surface with a helium beam.
According to such a semiconductor device, holes (excess carriers) within the drift layer can be vanished by recombination in the damaged region at the time of recovery of the diode device. As a result, the excess carriers contributing to a reverse current flowing through the diode device at the time of recovery can be decreased to be able to decrease the reverse current. Recovery characteristics of the diode device can thus be improved.